It is known that alkylbenzenes can be generated from alkylaryl alcohols by a process involving dehydration and hydrogenolysis. Substantial quantities of undesirable side products are usually generated from further reaction of alkylbenzene during the process.
It is also known that cumene (isopropylbenzene) can be generated from cumyl alcohol (2-phenyl-2-propanol) by a multiple-step process which involves dehydration to α-methyl styrene followed by the hydrogenation to cumene by a hydrogenolysis fixed-bed reaction, and the subsequent fractional distillation step to recover cumene. Substantial quantities of i-propylcyclohexane and cumene dimer are produced as undesirable by-products because alpha-methylstyrene (“AMS”) and cumene can stay on the hydrogenation bed after they are produced, (before exiting the catalyst bed) resulting in the further hydrogenation or dimerization thereof.
U.S. Pat. No. 6,455,712, WO 02/48126, WO 02/48125, and WO 02/48127 assigned to Shell Oil Company, disclose a process for reacting an alkylaryl hydroperoxide(s), such as obtained from cumene or dialkyl aryl, with an olefin to obtain a product stream comprising an oxirane compound and an alkylaryl hydroxyl compound, such as cumyl alcohol (also known as 2-phenyl-2-propanol) or p-di-(2-hydroxy-2-propyl)benzene or 2-propyl-3(2-hydroxy-2-propyl)benzene. Alkylaryl hydroxyl compounds are dehydrated and hydrogenated to produce alkyl aryl(s), followed by fractional distillation to recover alkylaryls, such as cumene or dialkyl aryl. 0.1–10 wt. % of i-propylcyclohexane is produced as undesirable side product. It is difficult to separate this impurity from cumene by fractional distillation due to the proximity of their boiling points.
WO 01/70714, assigned to Sumitomo, describes a process relating to oxidizing cumene to obtain isopropylbenzene peroxide as an oxygen carrier for the epoxidation of propylene to produce propylene oxide and cumyl alcohol. The cumyl alcohol is dehydrated and hydrogenated, via a hydrogenolysis step, to cumene and recycled for repeated use. During the hydrogenolysis step, up to 5 wt % of cumene is dimerized to produce cumene dimer, an undesirable by-product.
It is therefore desirable to develop a more efficient process which combines the multiple-step process into fewer steps and yet selectively produces a more pure cumene product with a smaller quantity of undesirable by-products.